The invention relates to the design of drivers for flat acoustic panels, in particular the design of drivers that can be used as pre-fabricated components with a large number of acoustic panels.
Conventional acoustic panels are known that operate according to the multi-resonance principle, frequently also referred to as multi-resonance plate loudspeakers. Further details of these devices are disclosed in the applications DE-A-197 57 097 to 197 57 099. To avoid unnecessary repetition, the application documents are incorporated herein by reference.
To produce bending waves in an acoustic panel, the panel is excited by one or several electrodynamic drivers (shakers). Other acoustic panels are known that are driven by piezoelectric bending oscillation disks, either exclusively or in combination with the aforedescribed electro-dynamic drivers. The subject matter of the present application, however, applies only the electro-dynamic drivers.
These drivers are formed essentially of an oscillation coil support, at least one permanent magnet and a short-circuit arrangement. The different components are arranged relative to one another so that the oscillation coil projects into an existing air gap. It should also be mentioned that the short-circuit arrangement should be understood as also including devices that merely direct or guide magnetic fields lines. Moreover, in the context of the present application, the air gap should not be understood as only including the gap between components adapted to receive an oscillation coil support and/or the oscillation coil.
The acoustic panel and the electro-dynamic drivers are combined in such a way that the drivers are placed on one side of the acoustic panel or integrated with the panel. If the drivers are placed on one side of the acoustic panel, then driver designs can be used that are also suitable driving cone loudspeakers. More particularly, the unit formed of the short-circuit arrangement and the respective permanent magnets is connected to the acoustic panel with support elements. In this embodiment, the oscillating coil which operates on the acoustic panel and is hence connected with the acoustic panel, can be centered by using centering membranes commonly found in cone loudspeakers. The centering membrane that is connected with the oscillating coil support is herein attached to the support elements. Although these units can be produced inexpensively and in large quantities making use of conventional manufacturing techniques for cone loudspeakers, it is disadvantageous to use these drivers with flat acoustic panels. The attached driver not only increases the depth of the unit, but the support members required with this driver design also increase the stiffness of the acoustic panel, which in turn hinders the generation and propagation of bending waves in the acoustic panel.
For these reasons, other recent designs have attempted to eliminate the support elements and integrate the drivers in the acoustic panel. Such devices are described in DE-A-197 57 097. An important aspect of these devices is that the oscillating coil support and/or the oscillating coil are not connected with the other components of the drivers (short-circuit arrangement, permanent magnet). This makes the design of such devices extraordinarily complex in order to prevent the oscillating coil support and/or the oscillating coil from coming in friction contact with the other components of the driver during operation. This problem may be solved by using a centering membrane known from cone loudspeaker technology and placed between the oscillating coil support and the acoustic panel, as depicted in FIG. 1 of DE-A-197 57 097. However, this solution still leaves another problem, namely to provide a snug association between the remaining components of the drivers (=the element 14.4 in FIG. 1 of DE-A-197 57 097) and the oscillating coil in the acoustic panel, when the drivers are disposed in the acoustic panel.
It is therefore an object of the invention to provide a driver for an acoustic panel, wherein the driver can be pre-produced for a number of different applications and integrated in the acoustic panel without requiring further centering steps.
By connecting the oscillating coil support in the air gap with the permanent magnet and/or the short-circuit arrangement, a driver is produced that can be integrated in an acoustic panel without requiring additional centering steps.
Since the bottom of the short-circuit arrangement facing away from the permanent magnet is provided with an armature plate and connected through the armature plate with the acoustic panel, assembly of the driver becomes much simpler.
Unlike conventional annular oscillating coil supports, the acoustic panel can be excited over a relatively large-area by forming the oscillating coil support in the shape of a coaxial cylinder, and by connecting to the bottom of the oscillating coil support with the acoustic panel.
The latter is true in particular when the bottom itself, or a plate disposed between the bottom and the acoustic panel, has a diameter that is smaller than or equal to the diameter of the oscillating coil support.
Advantageously, the bottom itself or the plate can be formed as a piezoelectric bending wave oscillator, since the close spacing between two drivers the contact facilitates contact between the drivers. To prevent the driver and the piezoelectric bending wave oscillator from interfering with each other, the piezoelectric bending wave oscillator should be connected with the oscillating coil support of the driver in a decoupled fashion.
If the edge of the oscillating coil support has a region with a decreased wall thickness and if the oscillating coil is connected with the oscillating coil support in this region, then large forces can be transmitted due to the solid design of the machines which are designed for winding oscillating coils on thin wall oscillating coil supports. The transition from the region of decreased wall thickness to the remaining edge of the oscillating coil support can have the form of a step that provides an additional interlocked engagement of the oscillating coil, which decreases the risk that the oscillating coil becomes detached from the oscillating coil support even if large forces are transmitted.
It should be pointed out that an oscillating coil support designed in a manner described above can be used by itself.